The mass flow rate of a rarefied gas through a long tube caused by large drops of the pressure and temperature has been calculated. The temperature ratio T-2/T-1=3.8, which is usually realized in practice, and the three Values of the pressure ratio (P-2/P-1=3.8, 10, and 100) have been taken. it has been found that the application of the linear theory based on the average rarefaction parameter to the nonisothermal gas flow reveals the error to be within 10%.